Voltage regulator with power rail tracking

Abstract

Disclosed herein are related to an integrated circuit to regulate a supply voltage. In one aspect, the integrated circuit includes a metal rail including a first point, at which a first functional circuit is connected, and a second point, at which a second functional circuit is connected. In one aspect, the integrate circuit includes a voltage regulator coupled between the first point of the metal rail and the second point of the metal rail. In one aspect, the voltage regulator senses a voltage at the second point of the metal rail and adjusts a supply voltage at the first point of the metal rail, according to the sensed voltage at the second point of the metal rail.

What is claimed is: 
     
       1. An integrated circuit comprising:
 a single metal rail configured to provide a plurality of functional circuits with a supply voltage, wherein the single metal rail has a first point and a second point, with the plurality of functional circuits disposed between the first and second points, and wherein one or more parasitic resistances are present between the first point and the second point; 
 a voltage regulator coupled between the first point and the second point of the single metal rail; and 
 wherein the voltage regulator is configured to adjust the supply voltage according to a voltage sensed at the second point. 
 
     
     
       2. The integrated circuit of  claim 1 , wherein at least one of the plurality of functional circuits includes an active circuit. 
     
     
       3. The integrated circuit of  claim 1 , wherein the voltage regulator includes a first transistor including:
 a drain electrode coupled to the first point of the single metal rail; and 
 a gate electrode coupled to the second point of the single metal rail. 
 
     
     
       4. The integrated circuit of  claim 3 , wherein the first transistor is configured to:
 sense the voltage at the second point through the gate electrode; and 
 adjust the supply voltage at the first point of the single metal rail through the drain electrode, according to the voltage sensed at the second point. 
 
     
     
       5. The integrated circuit of  claim 4 , wherein the voltage regulator further includes:
 a second transistor including a drain electrode coupled to a source electrode of the first transistor, the second transistor to enable or disable current through the first transistor according to a control signal. 
 
     
     
       6. The integrated circuit of  claim 5 , wherein the second transistor includes a source electrode coupled to another metal rail providing another voltage at the another metal rail higher than the supply voltage. 
     
     
       7. The integrated circuit of  claim 6 , wherein the first transistor is a P-type transistor. 
     
     
       8. The integrated circuit of  claim 5 , wherein the second transistor includes a source electrode coupled to another metal rail providing another voltage at the another metal rail lower than the supply voltage. 
     
     
       9. The integrated circuit of  claim 8 , wherein the first transistor is a N-type transistor. 
     
     
       10. The integrated circuit of  claim 5 , wherein the voltage regulator further includes a third transistor coupled to the first transistor in parallel, the first transistor of a first type, and the second transistor of a second type. 
     
     
       11. The integrated circuit of  claim 10 , wherein the third transistor includes:
 a source electrode coupled to the drain electrode of the first transistor, and 
 a drain electrode coupled to the source electrode of the first transistor. 
 
     
     
       12. The integrated circuit of  claim 11 , wherein the third transistor includes a gate electrode coupled to a source electrode of the second transistor. 
     
     
       13. The integrated circuit of  claim 11 , wherein the third transistor includes a gate electrode coupled to the drain electrode of the second transistor. 
     
     
       14. An integrated circuit comprising:
 a switch coupled between a first metal rail and a second metal rail, a first supply voltage present on the first metal rail and a second supply voltage present on the second metal rail; and 
 a first transistor coupled between the second metal rail and a third metal rail, a third voltage present on the third metal rail, the third metal rail coupled to one or more functional circuits; 
 wherein the first transistor is configured to regulate the third voltage based on a voltage difference between i) the first supply voltage or the second supply voltage, and ii) the third voltage. 
 
     
     
       15. The integrated circuit of  claim 14 , wherein the first transistor includes:
 a gate electrode coupled to the first metal rail; 
 a source electrode coupled to the third metal rail; and 
 a drain electrode coupled to the second metal rail. 
 
     
     
       16. The integrated circuit of  claim 14 , further comprising a second transistor coupled in parallel with the first transistor between the second metal rail and the third metal rail. 
     
     
       17. The integrated circuit of  claim 16 , wherein the first transistor is a first type of transistor, and the second transistor is a second type of transistor. 
     
     
       18. The integrated circuit of  claim 16 , wherein the one or more functional circuits are coupled between a first point of the third metal rail and a second point of the third metal rail, and
 wherein the second transistor includes:
 a gate electrode coupled to the second point of the third metal rail; 
 a drain electrode coupled to the first point of the third metal rail; and 
 a source electrode coupled to the second metal rail. 
 
 
     
     
       19. A method comprising:
 detecting a change in a first supply voltage supplied along a first metal rail; 
 adjusting a transconductance of a transistor based on a voltage difference between the first supply voltage at the first metal rail and a second supply voltage at a second metal rail; and 
 regulating the first supply voltage according to the adjusted transconductance. 
 
     
     
       20. The method of  claim 19 , further comprising:
 receiving, at a drain electrode of the transistor coupled to the second metal rail, the second supply voltage; and 
 providing, at a source electrode of the transistor coupled to the first metal rail, the first supply voltage.